That's the argument of Liberal Democrat David Leyonhjelm who on Wednesday introduced a private senator's bill to allow same-sex marriage.

The bill would allow any Australian to marry regardless of "sex, sexual orientation and gender identity".

However, it also gives non-government religious and civil celebrants the right to refuse to marry same-sex couples.

The libertarian doesn't believe government should interfere in individual choices and freedoms, and also supports the medical use of marijuana and assisted suicide.

Banning same-sex marriage diminishes people's ability to make life plans and marriage equality keeps state power in check, he says.

"The state is a wonderful servant but a terrible master," he says.

"The state cannot discriminate, and if it does so, that is an abuse of power."

He claims Prime Minister Tony Abbott counselled him against introducing the bill because it would cause more trouble for the government.

The Abbott government is under fire over a series of blunders and unpopular budget measures.

Mr Abbott promised pre-election to empower his party room to decide whether the coalition has a conscience vote on same-sex marriage, and Senator Leyonhjelm believes there is enough support for that to occur.

But the prime minister wants the bill abandoned, rather than allow it to proceed after coalition MPs are allowed a conscience vote, Senator Leyonhjelm said.